How to Design Reliable Microvias in Your PCBs

Originally published at:

Microvia failure occurs due to the thermal stresses that arise during the PCB assembly process. These stresses can have a significant impact on the reliability of the plated hole. Key design strategies for enhancing microvia reliability include selecting suitable materials for laser drilling, adhering to IPC-T-50M guidelines, and implementing stack-up configurations in alignment with IPC-2226 standards. Highlights: Factors contributing to microvia failures include the use of high-temperature dielectric materials and expansion rate mismatch during reflow. IPC-TM-650 2.6.27 and methods offer comprehensive microvia testing procedures. The change in microvia resistance during the reflow cycle should not exceed 5% of theā€¦

How does the choice of dielectric material impact the efficiency of laser drilling in PCB design, and what considerations should designers keep in mind for optimal results?

In microvia design, what advantages do staggered configurations offer over stacked ones, and how can we enhance the reliability of PCBs during thermal cycles?

The dielectric material significantly influences laser drilling efficiency. Optimal results are achieved by selecting materials like Isola FR408HR, FR370HR, I-speed, or Nelco N7000-2HT, known for being laser drillable. You should ensure material homogeneity in the stack-up to prevent uneven heating and inconsistencies, ultimately facilitating controlled-depth laser drilling.

Staggered microvias outperform stacked counterparts in withstanding thermal cycles. Their strategic arrangement ensures greater reliability by minimizing the impact of thermal expansion. Designers should maintain a minimum 2 mil spacing, predominantly fill external layer vias for cost efficiency, and ensure vertical separation between centers greater than the hole diameter for optimal results.